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首页> 外文期刊>Journal of mass spectrometry: JMS >Investigation of the afterglow time regime in pulsed radiofrequency glow discharge time-of-flight mass spectrometry
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Investigation of the afterglow time regime in pulsed radiofrequency glow discharge time-of-flight mass spectrometry

机译：脉冲射频辉光放电飞行时间质谱中余辉时间范围的研究

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摘要

The pulsed power operation mode of a radiofrequency (rf) glow discharge time-of-flight mass spectrometer was investigated, for several ions, in terms of intensity profiles along each pulse period. Particular attention was paid to the plateau and transient afterglow regions. An rf pulse period of 4 ms and a duty cycle of 50% was selected to evaluate the influence of discharge parameters in the afterglow delay and shape of Ar~+, Ar-2~+ and several analytes (Br, Cl, Cu) contained in polymeric layers. Pulse shapes of Ar~+ and Ar_2~+ ions vary with pressure and power. At low pressures the highest intensity is observed in the plateau while at higher pressures (>600 Pa) the afterpeak is the dominant region. Although the influence of the applied power is less noticeable, a widening of the afterglow time regime occurs for Ar~+ when increasing the power. Maximum intensity of the argon signal is measured in the afterglow at 30 W, while the area of such afterpeak increases with power. The maximum intensity of Ar_2~+ is obtained at the highest power employed (60 W) and the ratio maximum intensity/afterglow area remains approximately constant with power. Analytes with ionization potentials below (Cu) or just above (Br) the argon metastable energy show maxima intensities after argon ions decay, indicating they could be ionized by collisions with metastable Ar atoms. Chlorine signals are observed in the afterglow despite their ionization potential is well above the energy of argon metastable levels. Moreover, they follow a similar pattern to that observed for Ar_2~+, indicating that charge-transfer process with Ar_2~+ could play a significant role.
机译：针对沿每个脉冲周期的强度分布，对几种离子研究了射频（rf）辉光放电飞行时间质谱仪的脉冲功率操作模式。特别注意高原和短暂余辉区。选择4 ms的rf脉冲周期和50％的占空比以评估放电参数对余辉延迟和Ar〜+，Ar-2〜+以及所含几种分析物（Br，Cl，Cu）的形状的影响在聚合物层中。 Ar〜+和Ar_2〜+离子的脉冲形状随压力和功率而变化。在低压下，高原地区观测到最高强度，而在高压下（> 600 Pa），后峰是主要区域。尽管施加功率的影响不太明显，但是当增加功率时，Ar〜+会出现余辉时间范围的扩大。氩信号的最大强度是在30 W的余辉中测量的，而这种余峰的面积随功率的增加而增加。 Ar_2〜+的最大强度是在使用的最高功率（60 W）下获得的，并且最大强度/余辉面积之比随功率保持大致恒定。电离势低于（Cu）或刚好高于（Br）的分析物，氩亚稳能在氩离子衰减后显示出最大强度，表明它们可以通过与亚稳Ar原子的碰撞而被电离。尽管余氯的离子化电势远高于氩亚稳能水平，但仍能在余辉中观察到氯信号。此外，它们遵循与Ar_2〜+相似的模式，表明Ar_2〜+的电荷转移过程可能起重要作用。

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